Field of the Invention
The present invention relates to a liquid storage unit to be used in a liquid discharge apparatus configured to discharge liquid onto a recording medium, and more particularly, to a mechanism for removing bubbles from a liquid storage unit.
Description of the Related Art
A liquid discharge apparatus including a liquid tank and a liquid storage chamber configured to hold liquid supplied from the liquid tank and supply the liquid to a liquid discharge head is publicly known. Air may enter the liquid storage chamber due to various factors. The air may cause decrease in filling efficiency of the liquid from the liquid tank to the liquid storage chamber, and the entry of air to the liquid discharge head may affect the discharge. In Japanese Patent Application Laid-Open No. 2008-290419 and Japanese Patent Application Laid-Open No. 2002-370374, a liquid discharge apparatus including a liquid storage chamber having a bellows structure and a mechanism for expanding and contracting the liquid storage chamber in its axial direction is disclosed. When this mechanism is actuated, the entire liquid storage chamber is expanded and contracted, thereby being capable of discharging the air stagnating in the liquid storage chamber to the liquid tank.
In the liquid discharge apparatus disclosed in Japanese Patent Application Laid-Open No. 2008-290419 and Japanese Patent Application Laid-Open No. 2002-370374, the entire liquid storage chamber needs to be expanded and contracted, thereby being difficult to increase the thickness of the liquid storage chamber. Also in the bellows structure, it is preferred that the liquid storage chamber be thinner for the purpose of securing sufficient flexibility. On the other hand, the thin liquid storage chamber has high air permeability, and hence air is liable to enter the liquid storage chamber. The air thus having entered is mixed with liquid to become bubbles and stagnate in the liquid storage chamber. As a result, the frequency of the process of discharging the bubbles in the liquid storage chamber toward the liquid tank is increased. When a thick structure is employed for the purpose of reducing the air permeability of the liquid storage chamber, the liquid storage chamber cannot be expanded and contracted satisfactorily, thereby being difficult to discharge the bubbles in the liquid storage chamber to the liquid tank.